sup of gal induction

I don't have an answer, but do have a similar observation: when
expressing two different genes that have obvious (positive) growth
phenotypes, using heterologous promoters, the expression (i.e.
phenotypes) is good on plates: poor growth without the inducer, good
growth with the inducer. But the results are not the same when cells
grown in liquid medium; the cells behave as though the expression is
constitutively rather high. The promoters are CUP1 and the rat
glucocorticoid receptor (constitutively expressed from the GPD
promoter)/GRE/deoxycortisone system of Keith Yamamoto. Why the
difference?
Thanks,
Arle